Image processing apparatus, image processing method, and storage medium

ABSTRACT

Color image data is inputted, flag data indicative of attributes (character image, figure image, mesh image) of each pixel of an inputted image is generated, image processes, an enlargement, and a reduction according to the flag data are executed, the processed data is outputted to a printer, and an image of a high quality is formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an image processing apparatus and an imageprocessing method for performing a pixel density conversion of an imageand to a storage medium.

2. Related Background Art

Hitherto, what is called a color original copying apparatus as shown inFIG. 10 has been known as a system for digitally reading a colororiginal image and generating a copy image.

In FIG. 10, reference numeral 1001 denotes an image scanner for readingan original and performing a digital signal process, and 1002 indicatesa printer. An image corresponding to an original image read by the imagescanner 1001 is printed and outputted onto a paper in a full color bythe printer 1002. In the image scanner 1001, reference numeral 1000denotes a mirror surface pressure plate. An original 1004 put on acopyboard glass (hereinafter, referred to as a platen) 1003 isirradiated by lamps 1005 and an obtained image is guided to mirrors1006, 1007, and 1008. An image is formed by a lens 1009 onto asolid-state image pickup device sensor (hereinafter, referred to as CCD)1010 of three lines. Three image signals of red (R), green (G), and blue(B) as full color information are sent to a signal process unit 1011.The lamps 1005 and mirror 1006 are mechanically moved in the directionperpendicular to the electric scanning (main-scan) direction of the linesensor at a speed v, and the mirrors 1007 and 1008 are mechanicallymoved in the direction perpendicular to the electric scanning(main-scan) direction of the line sensor at a speed (½)v, therebyscanning (sub-scan) the whole surface of the original. The original 1004is read at a resolution of 600 dpi (dots/inch) in both main-scan andsub-scan.

The signal process unit 1011 electrically processes the read imagesignal, separates it into color components of magenta (M), cyan (C),yellow (Y), and black (Bk), and sends them to the printer 1002. A colorcomponent of one of M, C, Y, and Bk is sent to the printer 1002 withrespect to one scan of the original in the image scanner 1001. Oneprint-out operation is completed by scanning the original four times intotal.

Pixel signals of M, C, Y, and Bk sent from the image scanner 1001 aretransmitted to a laser driver 1012. The laser driver 1012 modulates asemiconductor laser 1013 in accordance with the transmitted imagesignals. A laser beam scans the surface of a photosensitive drum 1017through a polygon mirror 1014, an f-θ lens 1015, and a mirror 1016.Image data is written at a resolution of 600 dpi (dots/inch) in bothmain-scan and sub-scan in a manner similar to the reading mode.

Reference numeral 1018 denotes a rotary developer comprising a magentadevelopment unit 1019, a cyan development unit 1020, a yellowdevelopment unit 1021, and a black development unit 1022. The fourdevelopment units are alternately come into contact with thephotosensitive drum 1017, thereby developing an electrostatic latentimage formed on the photosensitive drum by toners.

Reference numeral 1023 denotes a transfer drum. The paper which is fedfrom a sheet cassette 1024 or 1025 is wound around the transfer drum1023, thereby transferring the images developed on the photosensitivedrum onto the paper.

After the images of four colors of M, C, Y, and Bk were sequentiallytransferred as mentioned above, the paper passes through a fixing unit1026, the toners are fixed onto the paper, and thereafter, the paper isdelivered.

According to the conventional example as described above, it isfundamentally necessary that the image scanner for reading the originaland the printer for outputting a copy image synchronously operate. Thatis, the image signals of R, G, and B read by the CCD sensor areprocessed every pixel by the signal process unit, converted into imagesignals of M, C, Y, and Bk, successively sent to the printer, andwritten onto the photosensitive drum by the laser beam, thereby formingthe copy image.

In the conventional example, one of M, C, Y, and Bk is used for formingthe image and the image forming process is repeated with respect to eachcolor, so that the original is continuously read four times.

It is not always necessary to continuously perform the reading operationof the original four times but there is also a construction such thatthe image data which was read only once is stored in temporary storingmeans and the stored image data is read out and outputted synchronouslywith the image formation of each of M, C, Y, and Bk.

However, although there is no need to store the image data into thestoring means in the former construction, the scanner and printer needto simultaneously operate. Therefore, for example, in the case where aheating unit of the fixing unit (in case of an ordinary thermal fixingtype) of the printer is not sufficiently heated, since the printer is ina standby mode, the copying operation and the original reading operationcannot be performed.

In case of copying a plurality of copies of each of a plurality oforiginals, it is necessary to perform the operation for reading oneoriginal plural times in correspondence to the output of a plurality ofcopies. The reading operation has to be performed with respect to eachof a plurality of originals. Thus, a time which the user has to expendfor such a purpose is very long.

In the latter construction, the scanner and printer can perform theoriginal reading operation asynchronously and, also in case ofoutputting a plurality of copies, it is sufficient to perform theoriginal reading operation once per original. However, since an amountof image data to be stored in the storing means is extremely large, itis difficult to simultaneously store a plurality of original images.Therefore, if it is intended to read a plurality of original images in alump and realize an exchange of pages, a synthesis output of a pluralityof original images, or the like after completion of the readingoperation, a storage device of a very large capacity is needed and it isnot practical. It is also impossible to perform a layout synthesis byenlargement and reduction of the stored image data.

In the case where it is intended to perform the optimum process inconsideration of a feature of the image data, it is necessary to detectthe feature of the image. A point of making handling of the image easyand outputting the image of a high quality in case of performing thelayout synthesis by the enlargement and reduction in the process usingthe feature data is not sufficiently examined.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an image processingapparatus and its control method, in which the above problems can besolved.

Another object of the invention is to provide an image processingapparatus and its control method, in which an image output of a highquality can be outputted while reducing a memory capacity of an image.

Still another object of the invention is to provide an image processingapparatus and its control method, in which the same image processes canbe performed for a copy of an original image and an image output of datafrom a computer.

Further another object of the invention is to provide an imageprocessing apparatus and its control method, in which proper imageprocesses can be performed for each of parts constructing an image andan image output of a high quality can be performed.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic construction of an imageprocessing apparatus to which the invention can be applied;

FIG. 2 is a diagram showing an example of an original image;

FIG. 3 is a diagram for explaining an example of an image area dividingprocess;

FIGS. 4A, 4B, and 4C are diagrams for explaining an example of flagdata;

FIG. 5 is a diagram for explaining an example of a layout synthesisoutput;

FIG. 6 is a block diagram showing an example of an output imageprocessing construction;

FIGS. 7A, 7B, 7C, and 7D are diagrams for explaining an example of apixel density converting method;

FIG. 8 is a diagram for explaining an example of a process in a2-dimension of the pixel density converting method;

FIGS. 9A and 9B are diagrams for explaining an example of an offsetprocess in the pixel density converting method;

FIG. 10 is a diagram for explaining a conventional color image copyingapparatus; and

FIG. 11 is a block diagram showing a schematic construction of an imageprocessing apparatus to which the invention can be applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT First Embodiment

An embodiment of the invention will now be described hereinbelow withreference to the drawings.

FIG. 1 is a block diagram showing an example of a construction of acopying apparatus of the first embodiment.

(Reading Unit)

An original to be copied is put on a copyboard glass (corresponding to1003 in FIG. 10) of a scanner 101 and read. As shown in FIG. 10, thescanner digitally reads an image of the original every pixel by a 3-linecolor CCD and transfers color image signals to an input image processunit 102. In the input image process unit 102, well-known imageprocesses such as shading correction, CCD inter-line correction, colorcorrection, and the like are performed to the RGB color image signalssent from the scanner.

Reference numeral 103 denotes a block for performing an image areadividing process to the image processed color image signals which areoutputted from the input image process unit 102. This block is an imagearea division process unit for detecting a feature of an image such asphotograph area, character area, mesh area, or the like every pixel ofthe input image and generating flag data indicative of attributes ofeach image area.

(Image Area Dividing Process)

The image area division process unit will now be described. The imagearea dividing process is performed for extracting a feature of theoriginal image in order to perform optimum image processes in accordancewith the feature of the image included in the original image andgenerating a signal showing the image area attributes (hereinafter, sucha signal is referred to as flag data). For example, various image areassuch as full color photograph area of continuous gradation, characterarea of monochromatic color of black, mesh print area like a newspaperprint, and the like exist mixedly in the original. If those image areasare uniformly processed by a same image processing procedure andresultant data is outputted, a preferable picture quality cannot beobtained in many cases. To solve such a problem, therefore, in the firstembodiment, FIG. 2 shows a specific procedure for detecting attributesof the image data included in the original image by using the colorimage signals processed by the input image process unit 102 andgenerating flag data for identifying the detected attributes.

FIG. 2 shows an example of an original image and illustrates a statewhere a silver salt photograph area 202, a black character area 203, amesh print area 204, and a color graphic area 205 exist mixedly in onepage 201. The scanner scans the original image by the color CCD sensorand reads it as color digital signals (R, G, B) of each pixel. The readRGB signals have a feature which is determined in dependence on theattributes of each area of the image. If the G signal among signalvalues (R, G, B) read by the CCD sensor in each area is plotted in thepixel arranging direction of the CCD, for example, a diagram as shown inFIG. 3 is obtained. In FIG. 3, reference numerals 302, 303, 304, and 305denote examples of characteristics which characteristically appear inthe case where the areas 202 to 205 in FIG. 2 are read. An axis ofabscissa denotes a pixel position in the pixel arranging direction ofthe CCD and an axis of ordinate indicates the read signal value. As thevalue approaches upward, the nearer the pixel approaches white (bright).

The feature of each area will be described. In case of the silver saltphotograph area 202, the change 302 in image signal depending on thereading position is relatively gentle and a difference 312 of the pixelvalues of the pixels existing at a short distance is small. Referencenumeral 303 denotes the characteristics of the black character area 203.Since black characters are written on a white background, a plot of itssignal value shows characteristics such that the read signal valuesuddenly changes in a range from a white background portion 313 to acharacter portion 323. Reference numeral 304 denotes the characteristicsof the mesh area 204. In case of the mesh area, since the whitebackground 314 and a mesh 324 printed thereon are repeated, a plot ofthe signal value shows characteristics such that black and white arerepeated at a high frequency as shown in the diagram. Reference numeral305 denotes the plot diagram of a graphic area. In an edge portion 315of graphic, the signal value suddenly decreases and an internal coloringportion 325 indicates characteristics such that a predeterminedintermediate level continues.

To discriminate the above attributes, it is sufficient to detect thefeature of each area as described above from the read signal values anddiscriminate. For this purpose, it is possible to use a featureextracting method using a well-known method based on a change amount ofthe image data near a target pixel, an accumulation value of the changeamount in a predetermined interval, a luminance value (white backgroundor a colored background) of a peripheral pixel, the number of times ofchange from white to black of the image data in a predeterminedinterval, or the like and to use a well-known attribute discriminatingmethod based on the feature extracting method.

FIGS. 4A to 4C show an example of attribute flags formed for theoriginal image of FIG. 2 as mentioned above. Although three kinds offlags of a character flag, a figure flag, and a mesh flag are formedhere as attribute flags (flag data), the invention is not limited tothem. FIG. 4A shows the character flag. A pixel shown in black in thediagram is a pixel having a character attribute, a character flag=1 isformed, and the other area is set to a character flag=0 (white portionin the diagram). FIG. 4B shows the figure flag corresponding to an areawhere it is set to 1 in the graphic area and to 0 in the other area.FIG. 4C shows the mesh flag corresponding to an area where it is set to1 in the mesh area and to 0 in the other area.

Since the silver salt photograph area 202 does not correspond to any ofthose areas, all flags are set to 0 and it does not appear in FIGS. 4Ato 4C.

If the image attributes are detected every pixel by the above image areadividing processes, image processes according to the image attributesare subsequently executed by a second input image process unit 104. Inthe unit 104, for example, a process to emphasize a sharpness ofcharacters by emphasizing a high frequency component of the image can beperformed to the character area, a process to remove a moire componentthat is peculiar to the digital image by performing what is called a lowpass filter process can be performed to the mesh area, or the like.Those processes can be switched on a pixel unit basis in accordance withthe attribute flag data generated by the image area division processblock 103.

(Storage of Image Data)

The image data which was read by the scanner and subjected to thevarious input image processes and the attribute flag data formed by theabove procedure are temporarily stored in a first image memory 105 and afirst flag memory 106, respectively. In this instance, the image dataand the attribute flag data are stored as partial images as much as awhole image of one page of the original or as much as a predeterminedsize of one page.

The image data and attribute flag data which have temporarily beenstored are compressed by a data compression unit 109 and stored in astorage device 110. It is desirable that the storage device 110 is astorage medium such as a semiconductor storage medium which can beaccessed at a high speed. In the data compression unit 109, differentdata compressing processes are performed to the image data and the flagdata, respectively. That is, it is desirable that a high efficientcompressing process such as a JPEG compression such as to makedeterioration of the image inconspicuous is performed to the image datain consideration of the human visual characteristics although such aprocess is irreversible. On the other hand, it is preferable to use areversible compression system such as a JBIG compression to the flagdata because a dropout or change of the attribute flag information doesnot occur. The reduction of a data amount using the proper compressingmethod according to the kind of data can be realized by such aconstruction. In this manner, the image data and flag data to which thedifferent compressing processes have been performed are stored in thestorage device 110 on a page unit basis of the original. There is also acase where the stored data is written into an auxiliary storage device111. As an auxiliary storage device 111, it is preferable to use amedium such as a hard disk which can store a large amount of dataalthough a recording speed is slightly low. As mentioned above, by usingthe auxiliary storage device 111 such as a hard disk in addition to thestorage device 110, the original images of a number of pages can beefficiently stored and accumulated.

(Reading of Image Data)

The image data and attribute flag data stored in the storage device 110or auxiliary storage device 111 are read out in order to output themfrom a printer 117, the compression data is decompressed by a datadecompression unit 112, and they are written into a second image memory114 and a second flag memory 115, respectively. At this time, there is acase where pixel densities of the stored image data are converted inpixel density conversion units 113 a and 113 b. Such a pixel densityconversion is used, for example, in the case where the user wants toenlarge or reduce the stored image data and print it out or the casewhere the user wants to layout-synthesize images of a plurality ofstored pages onto one sheet of print output paper and output them as onepaper.

As an example of the synthesis output of a plurality of pages, there isa case as shown in FIG. 5. That is, it is assumed that two originalimages 501 and 502 have previously been stored in the storage device110. FIG. 5 relates to a case where those two sheets of images aresynthesized onto one output paper of the same size as that of theoriginal, thereby obtaining a print output as shown at 503. For thispurpose, the stored image data 501 is first read out from the storagedevice 110 and the compressed data is decompressed. The decompresseddata is reduced at a predetermined magnification by the first pixeldensity conversion unit 113 a, rotated counterclockwise by 90° by arotation process unit (not shown), and written into a predetermined areain the second image memory 114 (area corresponding to 504 in FIG. 5).

Subsequently, the image data 502 is read out from the storage device 110and similarly subjected to decompression, resolution conversion, androtating process. The resultant data is written into an areacorresponding to 505 in the second image memory 114. In this instance,flag data corresponding to originals A and B are also similarlysubjected to decompression, resolution conversion, and rotating process(the same magnification and the same rotating process as those for theimage data). The resultant data is written into a corresponding area inthe second flag memory 115. However, a pixel density converting process(reducing process) in this case is executed by the second pixel densityconversion unit 113 b. Since the image data is similarly zoomed androtated with respect to the corresponding flag data, even in case ofperforming a layout print, adaptive image processes, which will beexplained hereinlater, according to the flag data can be performed. Itis desirable to use different methods for the pixel density conversionof the image data and the pixel density conversion of the flag data. Forexample, a well-known method such as linear interpolating method,bicubic spline interpolating method, or the like can be used for theimage data. For the pixel density conversion of the flag data, it isdesirable to use a pixel density converting method such as a nearestneighborhood processing method or the like that is adapted to binarydata. The details will be explained hereinlater.

(Output of Image Data)

When the image data and flag data temporarily stored in the second imagememory 114 and second flag memory 115 reach a predetermined size, theyare transferred to an output image process unit 116. The output imageprocess unit 116 executes well-known image processes for printoutputting the RGB image data, namely, a luminance density conversion,an RGB→CMYK conversion, a gamma correction, a binarizing process, andthe like and transfers the processed data to the printer 117. On thebasis of the transferred image signals of CMYK, the printer 117 drivesthe semiconductor laser, and forms and outputs a visible image onto thetransfer paper by a well-known procedure.

The flag data stored in the second flag memory 115 is used for switchingthe processes which are executed in the output image process unit 116.That is, by making masking coefficients of the RGB→CMYK conversiondifferent in the photograph area and the character area, a picturequality of the output image can be improved. For example, conversioncoefficients such that black characters can be reconstructed only by theblack toner (that is, in the case where the image data is achromaticcolor, coefficients such that C, M, Y=0) are applied to the pixels inthe character area, namely, the character flag=1. Coefficients such thateven in case of the achromatic color, C, M, Y≠0 and deep black can bereconstructed can be applied to the other area.

In the binarizing process, the C, M, Y, and K signals are converted intobinary signals of 0 or 1 by using a well-known error diffusion processor dither process. However, since priority is given to a sharpness of anoutput image in the character area or graphic area at this time, theerror diffusion process is applied. Since importance is attached to agradation in the photograph or mesh area, the dither process is applied.By switching the contents of the binarizing process in accordance withthe attribute flag data in this manner, the picture quality of theoutput image can be improved.

FIG. 6 shows an example of a constructional block diagram for suchprocesses. The second image memory 114, second flag memory 115, andprinter 117 are the same as those in FIG. 1. The color image data of RGBread out from the second image memory 114 is inputted in parallel toRGB→CMYK converting circuits 601 and 602 and independently convertedinto the CMYK image signals, respectively. One of outputs of the CMYKconverting circuits 601 and 602 is selected by a first selector 603 inaccordance with a flag signal in the second flag memory 115. Ifconversion coefficients for the character area have been set in the CMYKconverting circuit 601 and coefficients other than the conversioncoefficients for the character area have been set in the CMYK convertingcircuit 602, the output of the CMYK converting circuit 601 is selectedwhen the character flag in the second flag memory 115 is equal to 1. Theoutput of the CMYK converting circuit 602 is selected when the characterflag=0.

An output of the first selector 603 is also separated in parallel intotwo systems. One of them passes through a first gamma correction circuit604 and an error diffusion binarization process unit 606 and is inputtedas a binary CMYK signal to a second selector 608. The output of thefirst selector 603 also passes through a second gamma correction circuit605 and a dither process binarizing circuit 607 and is also inputted asa binary CMYK signal to the second selector 608.

The second selector 608 selects an output of either the error diffusionprocess unit 606 or dither process unit 607 and transfers it to theprinter 117. Since the error diffusion process is selected for thecharacter area and flag area here, when the character flag=1 or figureflag=1, the second selector 608 selects the output of the errordiffusion process unit 606. In the other cases, the second selectorselects the output of the dither process unit 607.

(Pixel Density Conversion of Image Data)

The above pixel density converting method will be described in detail.Explanation will now be made with respect to a processing method in thecase where the image data and flag data which were decompressed by thedata decompression unit 112 are enlarged or reduced by the pixel densityconversion units 113 a and 113 b and outputted to the second imagememory 114 and second flag memory 115.

FIGS. 7A and 7B are graphs obtained by plotting the image data and flagdata which were read, respectively. An axis of abscissa denotes a pixelposition (coordinate) in the arranging direction of the CCD in the imagereader and an axis of ordinate indicates a pixel value (0 to 255) and aflag value (0 or 1) of the image, respectively. FIG. 7A shows, forexample, the G signal among the R, G, and B signals. FIG. 7B shows, forexample, the character flag among a plurality of flag data.

In the diagram, white circles 701 and 702 indicate data of one pixel,respectively. In the embodiment, since a reading resolution of the imagereader is equal to 600 dpi, an interval between the respective pixelscorresponds to 600 dpi (25.4/600 mm) as a value on the original.

A case of reducing such image data into, for example, 0.75 time will nowbe considered. (This magnification corresponds to a reduction ratio inthe example of FIG. 5). In this case, it is necessary to newly formpixel values at the positions shown by arrows of broken lines in thediagram and form the image data after the reduction. This processcorresponds to the process for reducing and thinning out three pixels ofthe original image data and forming data of two pixels. Therefore, ifthe coordinate after the reduction arrives at a position 703, it issufficient to set the original image data to the pixel values of theimage after the reduction as they are. However, when it reachespositions 704, it is necessary to perform an interpolating arithmeticoperation and form the data from the pixel values before and after thetarget pixel. If the linear interpolating method is used for thispurpose, the pixel values after the reduction become as shown by blackcircles in FIG. 7C. Since each pixel value 705 in the diagramcorresponds to the coordinate position 703, it is nothing but the pixelvalue of the inherent corresponding coordinate. However, since eachpixel value 706 corresponds to the coordinate 704, it is replaced with amean value of two adjacent pixels of the original pixel valuessandwiching the position of 704.

The above processes are executed by the first pixel density conversionunit 113 a.

A reducing process of the flag data will now be described. Since theresolution of the flag data is equal to that of the image data, FIG. 7Bshows the same pixel arrangement as that of FIG. 7A. The pixelcoordinate corresponding to the reduced data in case of reducing thedata into 0.75 time is set to a position shown by an arrow of a brokenline even in FIG. 7B in a manner similar to FIG. 7A. Therefore, althougha pixel value 709 corresponding to a coordinate 707 is nothing but thepixel value of the inherent corresponding coordinate in FIG. 7B, it isnecessary to arithmetically operate a pixel value 710 corresponding to acoordinate 708 from the neighboring pixel values (flag values) on bothsides of the pixel value 710 and form it.

However, since the flag data in FIG. 7B is binary information of 0 or 1,the foregoing linear interpolating method cannot be applied. Therefore,it is sufficient to use here a construction such that the pixel value(flag value) existing at the nearest distance position among theoriginal image coordinates corresponding to the pixel positions afterthe reduction is used as a pixel value after the reduction. This methodis called a nearest neighborhood reducing process.

However, if such a method is simply used, it will be understood that thepixel value corresponding to a pixel 711 of “1” in FIG. 7B is changed tothe pixel value 710 in FIG. 7D after completion of the conversion andhas been extinguished. Therefore, it is assumed that a processing methodwhereby the OR obtained by the neighboring flag values on both sides ofthe pixel position after the reduction is set to the flag value afterthe reduction is used. By using this method, the pixel value after thereduction becomes as shown at 712 and a situation such that the inherentflag information before the reduction is dropped out by the reducingprocess can be prevented.

The above processes are executed by the second pixel density conversionunit 113 b.

If the reduction image data and reduction flag data formed as mentionedabove are stored in the second image memory 114 and second flag memory115, a print output reduced by the procedure described above can beobtained.

Although the explanation has been made here on the assumption that theimage data and flag data are arranged as a one-dimensional array, thelinear zooming method can expand the image data to the 2-dimensionaldata as is well known. A zooming process of the flag data can be alsoexpanded to a 2-dimension. FIG. 8 is a diagram for explaining a casewhere the zooming method of the flag data has been expanded into the2-dimension. In the diagram, data shown by a white circle 801 indicatesflag data of the original image before the zoom and has a value of 0or 1. A black circle 802 indicates a position of a pixel to be formedafter the zoom (reduction in this case) and the data shown by the blackcircle also has a value of 0 or 1. Now, assuming that a position of thetarget pixel is located at 803, flag data after the zoom 803 can beobtained by getting the OR by using all of four original image flag data804 surrounding the target pixel 803. That is, 0 is formed as a targetpixel if all of the four pixels shown at 804 are equal to 0, and 1 isformed in the other cases.

Although the explanation has been made on the assumption that the pixelvalues after the zoom are formed by the OR process of the near pixels,the invention is not limited to such a case. For example, there areconsidered various methods such as method whereby only one nearest pixelis detected and set to the same value as that of the target pixel,method whereby the number of pixels of “1” among the peripheral nearpixels is counted and, if a count value is equal to or larger than apredetermined value, the pixel value after the zoom is set to 1, and thelike.

The forming (generating) method of the pixel value can be also changedafter the zoom in accordance with a zoom ratio. For example, it is alsopossible to perform processes such that if the zoom ratio is smallerthan 1 (reduction), the target pixel value is formed by the OR of aplurality of pixels near the target pixel, and if the zoom ratio islarger than 1 (enlargement), the pixel value of one pixel existing atthe nearest position of the target pixel is formed as a target pixelvalue as it is.

The forming method of the pixel value can be also changed after the zoomin accordance with attributes of the flag. Although three kinds of flagsof the character attribute, figure attribute, and mesh attribute havebeen shown in the embodiment, there is also a case where adiscrimination result about whether the OR process is suitable or thereplacement to only one near pixel is suitable upon reduction differsevery attribute. Therefore, for example, if the character flag andfigure flag are reduced by the OR process and the mesh flag is reducedby the process for replacing the target pixel value with the nearestneighboring pixel value, an effect such that an error decision flag inthe case where a mesh decision precision is not enough is eliminatedupon reducing process can be expected. If a method whereby the number ofpixels whose flag data is equal to 1 among the peripheral neighboringpixels is counted and if a count value is equal to or larger than apredetermined value, the pixel after the zoom is set to 1 is used forthe mesh flag, even if the mesh flag is erroneously equal to 1 in aregion out of the mesh area in the erroneous discrimination, since nomesh flag exists at positions around the target pixel, the count valueis not equal to the predetermined value or more and the influence by theerroneous decision can be eliminated.

It is also possible to use a construction such that a manual switchingunit for switching the interpolating method of the flag data and asampling instructing unit for allowing a sampling print (thumbnailprint) to be outputted are provided for the operation unit, the actualprint is executed in response to a sampling output instruction, and theoperator is allowed to select the interpolating method by a manualinstruction. Further, it is also possible to execute a process such thatan offset is given to sampling coordinates in the pixel densityconversion. FIGS. 9A and 9B are diagrams for explaining processes insuch a case.

FIG. 9A is a diagram for explaining a pixel density conversion of imagedata in a manner similar to that in FIG. 7A. A start position shown byan arrow corresponding to the pixel position after completion of thepixel density conversion has been shifted by ΔX as shown at 903. Aninterval between the arrows is the same as that shown in FIGS. 7A to 7D.

By using the above method, a situation such that the case where theinherent pixel value is outputted as it is and the case where theoriginal pixel values are interpolated and outputted alternately occuris eliminated and all output pixel values are formed by interpolationarithmetic operations between the neighboring adjacent pixels, so thatthere is a case where the picture quality is improved.

As mentioned above, in the case where the offset has been given to thesampling position by the first pixel density conversion unit, it isnecessary to also set the same offset value ΔX to the second pixeldensity conversion unit. Such a state is shown in FIG. 9B. A startposition 907 of the output pixel position is shifted by ΔX in a mannersimilar to the case of FIG. 9A.

Since a distance relation between the output pixel position and theoriginal pixel position is deviated in this case, the adjacent pixels onboth sides to be subjected to the OR calculation are different fromthose in FIGS. 7A to 7D and the corresponding position relation betweenthe pixel after the pixel density conversion of the image data and thepixel after the pixel density conversion of the flag data is preferablyheld.

Another Embodiment

Although a flow of the image data from the scanner 101 in FIG. 1 hasbeen described above, the processes in the first embodiment can be alsosimilarly applied to image data which is inputted from an externalcommunication path 119 through a communication interface 118.

As typical data which is sent from the external communication path 119,there is image data described by what is called PDL (page descriptionlanguage). The PDL data which is inputted here is a group of commandsdescribing an image. If PDL data is interpreted and converted into bitmap data similar to the scanner read image, it can be applied as it is.

That is, the PDL data inputted from the communication I/F 118 isconverted into an intermediate language format called a display list byan interpreter 108. The display list is sent to an RIP (raster imageprocessor) 107 and developed into bit map data. The developed image datais stored in the first image memory 105. At this time, the RIP 107 formsattribute information of the image data which was rasterizedsimultaneously with it as flag data and stores it into the first flagmemory 106.

In this instance, the process for forming the flag data by an image areadividing process with reference to the image data as described in thefirst embodiment is unnecessary here. It is sufficient to form the flagdata of the corresponding pixel of the rasterized image with referenceto the attribute information (information indicative of a photograph,characters, graphics, or the like) held every part in the PDL data whichis inputted to the RIP.

That is, if a PDL command to form character parts is inputted to the RIP107, it is sufficient that the RIP 107 forms a bit map image of thecharacter data and, at the same time, forms the character flag (=1) asflag data corresponding to the area where the character has been formed.If the image data and flag data were formed as mentioned above, thesubsequent processes can be executed in substantially the same manner asthose in the first embodiment.

Although two pixel density conversion units have been provided in FIG.1, the pixel density conversion can be also performed in one pixeldensity conversion unit as shown in FIG. 11.

Other Embodiments of the Invention

A processing method whereby a program for making the construction of theabove embodiment operative so as to realize the functions of theembodiment mentioned above is stored in a storage medium, the programstored in the storage medium is read out as codes, and operations areexecuted by a computer in accordance with the read-out program codes isalso incorporated in the purview of the foregoing embodiment. Thestorage medium in which the program has been stored is also incorporatedin the embodiment.

As such a storage medium, for example, a floppy disk, a hard disk, anoptical disk, a magnetooptic disk, a CD-ROM, a magnetic tape, anon-volatile memory card, or an ROM can be also used.

The invention is not limited to the example in which the processes areexecuted by the sole program stored in the storage medium but a casewhere the program operates on the OS in cooperation with anothersoftware and functions of an expansion board and the operations of theembodiment are executed is also incorporated in the purview of theforegoing embodiment.

As described above, a data output which makes the handling of the imageeasy and enables a high quality image output to be performed withoutbearing a heavy load on the user can be performed, and the image can beformed at an arbitrary zoom ratio. An image memory capacity can be alsosuitably determined in accordance with the kind of data to be stored.Further, the pixel density converting process can be also adaptivelyperformed and the improvement of the picture quality can be alsorealized.

The same processes can be performed in both case where the originalimage is read by the scanner and a print is outputted and case where aprint image using the PDL (page description language) is outputted. Theoptimum image processes can be performed to individual partsconstructing the image at an arbitrary zoom ratio. An output image of ahigh picture quality can be obtained in any case.

The present invention is not limited to the foregoing embodiments butmany modifications and variations are possible within the spirit andscope of the appended claims of the invention.

1. An image processing apparatus comprising: input means for inputtingcolor image data; generating means for generating flag data indicatingan attribute of an image corresponding to the color image data from thecolor image data, with respect to each pixel of the image, the flag dataindicative of a character, a figure or a mesh with respect to each pixelof the image; first pixel density converting means for pixel densityconverting the image data at a designated magnification; second pixeldensity converting means for pixel density converting the flag data inaccordance with the designated magnification; and output means formaking a process of the pixel density converted image data differentevery pixel in accordance with the flag data and outputting theprocessed image data, wherein a pixel converting method of said firstpixel density converting means is different from a pixel convertingmethod of said second pixel density converting means, said second pixeldensity converting means makes a converting method different inaccordance with attributes of the flag data, and said second pixeldensity converting means, when the designated magnification isreduction, performs an arithmetic operating process of flag values usinga plurality of pixels near a target pixel with respect to the flag dataindicative of a character and a figure, and performs a processing usinga nearest neighboring pixel of the target pixel, with respect to theflag data indicative of a mesh.
 2. An apparatus according to claim 1,wherein when the flag data is a character flag, said output meansperforms a sharpness emphasis to the image data.
 3. An apparatusaccording to claim 1, wherein when the flag data is a mesh flag, saidoutput means performs a low pass filter process to the image data.
 4. Anapparatus according to claim 1, wherein said generating means generatesthe flag data on the basis of a change in image data of a pixel near atarget pixel.
 5. An apparatus according to claim 1, wherein said firstpixel density converting means uses one of a linear interpolating methodand bicubic spline interpolation.
 6. An apparatus according to claim 1,wherein said output means makes a binarizing process to the image datadifferent in accordance with the flag data.
 7. An apparatus according toclaim 6, wherein when the flag data is the character flag or figureflag, an error diffusion process is performed to the image data.
 8. Anapparatus according to claim 1, wherein said output means changes colorconversion coefficients in accordance with the flag data and performs acolor converting process of the image data.
 9. An apparatus according toclaim 1, wherein in the case where said input means inputs datadescribed by a page description language from a computer, saidgenerating means generates the flag data on the basis of attributeinformation of the page description language.
 10. An image processingmethod comprising the steps of: inputting color image data; generatingflag data indicating an attribute of an image corresponding to the colorimage data from the color image data, with respect to each pixel of theimage, the flag data indicative of a character, a figure or a mesh withrespect to each pixel of the image; pixel density converting the imagedata at a designated magnification; pixel density converting the flagdata in accordance with the designated magnification; and making aprocess of the pixel density converted image data different every pixelin accordance with the flag data and outputting the processed image datato a printer, wherein a pixel converting method of said step of pixeldensity converting the image data is different from a pixel convertingmethod of said step of pixel density converting the flag data, said stepof pixel density converting the flag data includes making a convertingmethod different in accordance with attributes of the flag data, andsaid step of pixel density converting the flag data, when the designatedmagnification is reduction, includes performing an arithmetic operatingprocess of flag values using a plurality of pixels near a target pixelwith respect to the flag data indicative of a character and a figure,and includes performing a processing using a nearest neighboring pixelof the target pixel, with respect to the flag data indicative of a mesh.11. A computer-readable storage medium which stores a program forallowing an image processing apparatus to execute said programcomprising the steps of: inputting color image data; generating flagdata indicating an attribute of an image corresponding to the colorimage data from the color image data, with respect to each pixel of theimage, the flag data indicative of a character, a figure or a mesh withrespect to each pixel of the image; pixel density converting the imagedata at a designated magnification; pixel density converting the flagdata in accordance with the designated magnification; and making aprocess of the pixel density converted image data different every pixelin accordance with the flag data and outputting the processed image datato a printer, wherein said step of pixel density converting the flagdata includes making a converting method different in accordance withattributes of the flag data, and said step of pixel density convertingthe flag data, when the designated magnification is reduction, includesperforming an arithmetic operating process of flag values using aplurality of pixels near a target pixel with respect to the flag dataindicative of a character and a figure, and includes performing aprocessing using a nearest neighboring pixel of the target pixel, withrespect to the flag data indicative of a mesh.
 12. An image processingapparatus comprising: input means for inputting color image data;generating means for generating flag data indicating an attribute of animage corresponding to the color image data from the color image data,with respect to each pixel of the image, the flag data indicative of acharacter, a figure or a mesh with respect to each pixel of the image;first pixel density converting means for pixel density converting theimage data at a designated magnification; second pixel densityconverting means for pixel density converting the flag data inaccordance with the designated magnification; and output means formaking a process of the pixel density converted image data differentevery pixel in accordance with the flag data and outputting theprocessed image data, wherein a pixel converting method of said firstpixel density converting means is different from a pixel convertingmethod of said second pixel density converting means, said second pixeldensity converting means makes a converting method different inaccordance with attributes of the flag data, and said second pixeldensity converting means, when the designated magnification isreduction, performs an arithmetic operating process of flag values usinga plurality of pixels near a target pixel with respect to the flag dataindicative of a character and a figure, and performs a processing ofcounting the number of pixels of which flag data is 1 in the peripheralneighboring pixels and setting the pixel after the magnification changeto 1 if the counted value exceeds a predetermined value, with respect tothe flag data indicative of a mesh.
 13. An image processing methodcomprising the steps of: inputting color image data; generating flagdata indicating an attribute of an image corresponding to the colorimage data from the color image data, with respect to each pixel of theimage, the flag data indicative of a character, a figure or a mesh withrespect to each pixel of the image; pixel density converting the imagedata at a designated magnification; pixel density converting the flagdata in accordance with the designated magnification; and making aprocess of the pixel density converted image data different every pixelin accordance with the flag data and outputting the processed imagedata, wherein a pixel converting method of said step of pixel densityconverting the image data is different from a pixel converting method ofsaid step of pixel density converting the flag data, said step of pixeldensity converting the flag data makes a converting method different inaccordance with attributes of the flag data, and said step of pixeldensity converting the flag data, when the designated magnification isreduction, includes performing an arithmetic operating process of flagvalues using a plurality of pixels near a target pixel with respect tothe flag data indicative of a character and a figure, and includesperforming a processing of counting the number of pixels of which flagdata is 1 in the peripheral neighboring pixels and setting the pixelafter the magnification change to 1 if the counted value exceeds apredetermined value, with respect to the flag data indicative of a mesh.14. A computer-readable storage medium which stores a program forallowing an image processing apparatus to execute said programcomprising the steps of: inputting color image data; generating flagdata indicating an attribute of an image corresponding to the colorimage data from the color image data, with respect to each pixel of theimage, the flag data indicative of a character, a figure or a mesh withrespect to each pixel of the image; pixel density converting the imagedata at a designated magnification; pixel density converting the flagdata in accordance with the designated magnification; and making aprocess of the pixel density converted image data different every pixelin accordance with the flag data and outputting the processed imagedata, wherein a pixel converting method of said step of pixel densityconverting the image data is different from a pixel converting method ofsaid step of pixel density converting the flag data, said step of pixeldensity converting the flag data makes a converting method different inaccordance with attributes of the flag data, and said step of pixeldensity converting the flag data, when the designated magnification isreduction, includes performing an arithmetic operating process of flagvalues using a plurality of pixels near a target pixel with respect tothe flag data indicative of a character and a figure, and includesperforming a processing of counting the number of pixels of which flagdata is 1 in the peripheral neighboring pixels and setting the pixelafter the magnification change to 1 if the counted value exceeds apredetermined value, with respect to the flag data indicative of a mesh.